Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
School of Chemistry, Federal University of Rio de Janeiro, Av. Athos da Silveira Ramos, 149, Rio de Janeiro, RJ, 21941-909, Brazil.
Environ Sci Pollut Res Int. 2018 Oct;25(28):27808-27818. doi: 10.1007/s11356-018-2939-5. Epub 2018 Aug 21.
Polycyclic aromatic hydrocarbons (PAHs) are on the list of priority pollutants to be eliminated from the environment due to their carcinogenic and mutagenic action, chemical stability, and resistance to biodegradation. The aim of this study was to evaluate the degradation of fluorene, a well-known PAH, in aqueous solutions (0.03 and 0.08 mg L), by means of a solar-driven conventional (PF) and modified photo-Fenton mediated by ferrioxalate complexes (PFF). Photolysis was also employed for comparison purposes. PF reaction was evaluated at different pH values (2.8, 3.5, and 4.0) and iron concentrations (2, 5, 10, and 20 mg L). On the other hand, PFF studies were conducted at mild pH conditions (4.0, 5.0, and 6.0) and iron content of 2 mg L, keeping initial iron/oxalate molar ratio at 1:3. In both PF and PFF, the initial hydrogen peroxide/iron molar ratio was maintained at 5. In the presence of methanol as cosolvent for fluorene dissolution, the PF reaction was hampered and no consumption of HO was observed during the reaction carried out at constant pH (2.8). This led to low degradation rates, similar to those achieved by photolysis. Under the same pH but using acetonitrile as cosolvent for fluorene dissolution, fluorene degradation was found to be proportional to the iron content used in the PF experiments. On the other hand, at an invariable iron concentration of 5 mg Fe L, the increase in pH was accompanied by a decrease in the molar fraction of the most photoactive iron complex (FeOH) and ferric hydroxides precipitation, leading to a reduction in the fluorene degradation rate. With regard to the PFF tests, similar fluorene degradation performance was achieved at pH 4 and 5, while at pH 6 iron precipitation became relevant and the degradation rate was slightly slower. PFF has shown to be more efficient than the PF under the same pH (4) and iron concentration (2 mg L). Moreover, even at near neutral pH (6), fluorine degradation was shown to be feasible by using ferrioxalate complexes.
多环芳烃（PAHs）因其致癌性和致突变性、化学稳定性和抗生物降解性而被列入需要从环境中消除的优先污染物之列。本研究旨在评估在水溶液（0.03 和 0.08mg/L）中通过太阳能驱动的常规（PF）和铁草酸盐配合物介导的改良光芬顿（PFF）降解芴，光解也被用于比较目的。在不同的 pH 值（2.8、3.5 和 4.0）和铁浓度（2、5、10 和 20mg/L）下评估 PF 反应。另一方面，在温和的 pH 条件（4.0、5.0 和 6.0）和 2mg/L 的铁含量下进行 PFF 研究，保持初始铁/草酸摩尔比为 1:3。在 PF 和 PFF 中，均保持初始过氧化氢/铁摩尔比为 5。在甲醇作为芴溶解的共溶剂的存在下，PF 反应受到阻碍，并且在恒 pH（2.8）下进行的反应中没有观察到 HO 的消耗。这导致降解速率较低，类似于光解的降解速率。在相同的 pH 下，但使用乙腈作为芴溶解的共溶剂，发现 PF 实验中使用的铁含量与芴的降解成正比。另一方面，在不变的铁浓度为 5mgFeL 时，pH 的增加伴随着最光活性铁配合物（FeOH）的摩尔分数的降低和三价铁氢氧化物的沉淀，导致芴的降解速率降低。对于 PFF 测试，在 pH 4 和 5 时达到了相似的芴降解性能，而在 pH 6 时铁沉淀变得相关，降解速率略慢。在相同的 pH（4）和铁浓度（2mg/L）下，PFF 比 PF 更有效。此外，即使在接近中性的 pH（6）下，使用铁草酸盐配合物也可以实现氟的降解。
